The present invention concerns an apparatus for propulsion in oblong cavities and pipes; as stated in the preamble of the following claim 1.
By oblong cavities is meant pipes, ducts, drilled or mined holes in rock, or wells which are drilled with or without casing in the ground (oil related holes), in metals or other materials.
According to the invention the apparatus is used when inspection or different kind of work are performed in such cavities. According to the invention the apparatus may be used to force forward the equipment for boring the hole, but can also be used for pulling equipment through the cavity.
In such cavities, pipes and ducts, where it is not possible to use people there is often need for inspection, service, maintenance and other work to be done. It might also be necessary to increase the propelling power on the drilling equipment which is drilling holes/wells.
In vertical holes, for example in oil related wells, it is normal to pull the necessary equipment down into the well by means of gravity, if it is not pushed downward by means of a pipe. In horizontal holes or pipes where it is not possible to utilize gravity, an apparatus for pulling or pushing is required for the equipment to be transported. Different hydraulic methods to pump forward equipment have also been tested. The methods which are based on pipes for transporting the equipment, require a lot of space and personel to run it all day and night, and further the transportation speed is relatively low.
From British patent GB-1.328.886 a vehicle coupled to a coiled tubing is known, thus enabling the vehicle to pull or push the coiled tubing.
From British patent patent GB-2.196.715 a device which is driven forward by liquid or gas pressure through a pipeline is known.
From GB-2.200.970 a vehicle having motor powered wheels is known, but where propulsion may be provided also by means of chain and sprocket wheels.
From U.S. Pat. No. 4,941,511 a joint separated vehicle is known, where one part includes the energy source and the other part includes a motor connected to the driving wheels. A similar device is known from GB patent specification 2.122.713.
From EP patent specification 0.461.964 a vehicle where propulsion is generated by means of motor driven belts or wheels is known.
In DE patent specification 3.206.033 there is shown a vehicle where the propulsion is provided by means of an obliqued wheel, the wheel axis of which is mounted eccentric on an shaft shich is positioned centric of the vehicle. The wheel is therefore aligned mainly crosswise to the traction direction. Said eccentricity causes the wheel to be in contact with the pipe wall and the contact point moves as the shaft is rotated. The oblique position of the wheel causes that the movement of the contact point also generates propulsion. Further the vehicle is also equipped with radial directed wheels which abut the pipe wall for centring the vehicle inside the pipe line. Further the vehicle is equipped with radial directed wheals which abut the pipe wall for centering the vehicle inside the pipe, and for giving counter-torque to the drive motor.
From SU patent 481 784 a vehicle is known where several crosswise spring loaded wheels are mounted adjacent the surface of the vehicle so that the wheels abut the pipe wall and centers the vehicle within the pipe line. When the vehicle rotates around it""s own axis, the wheels cause a propulsion corresponding to the wheel angle. This apparatus need counter force torque.
From Norwegian Patent No. 178.276 a pipe tractor arranged to move within canals and pipes is known, in that the end portions of the tractor is mounted and equipped with spring loaded arms to which crosswise wheels are mounted, and the wheels abut the inner surface of the pipe, so that side force affecting the wheels provides for propulsion of the vehicle when the end portions are rotating. The end portions rotate in opposite directions related to each other, and one of the ends acts as counter torque for the other end, and visa versa.
From International patent PCT/GB93/0111 a down hole tool is known, for providing rotary support of a downhole assembly in which the tool is incorporated. The tool also converts rotary contact with the wellbore into a longitudinal force which turns the assembly along the wellbore. The tool comprises a stabiliser including rollers, wherein the roller axis are skewed to be tangential to a notional helix, such that the natural path of roller contact with the wellbore has a longitudinal component in addition to the usual circumferential path. The tool can be used on drill strings and in downhole assemblies with motor. The tool may also pull a cable supplying the tool with electricity/hydraulic power for the propulsion machinery.
The pulling-/pushing apparatus of today are encumbered with a lot of disadvantages. Firstly they are very complex, they have a limited operation range and they are produced for dedicated actions/tasks which they are intended to execute. There are also strict requirements regarding the surroundings in which they are used.
It is an object of the invention to prepare a new and improved propulsion apparatus for transporting (pushing/pulling) through pipes/cavities.
Further it is an object to produce an apparatus which may effect an increased pulling power, independent of the design of the cavity, and reduced demands to the strength/toughness of the inside wall of the pipe/cavity.
A further object is to produce an apparatus that can work without any counter torque. Finally it is an object to produce a shorter propulsion apparatus with lower weight, therefore being easier to handle, and may carry more equipment for each trip.
The apparatus of the present invention is characterized by the features which are defined in the characterizing clause of the following claim 1.
The preferred embodiments of the apparatus in accordance to the invention are stated in dependent patent claims.
With this invention an apparatus with a simple construction is designed, and which is easy to run and covers a large working area, and more specific the apparatus may operate in ducts having very variable cross section and variable diameter, that is to say within the working range of the apparatus within the maximum and minimum diameters for its operation. The apparatus involves a simple design so that different sizes of it may pull/push i holes having diameter ranges of millimeter to several meters.
The apparatus is further designed for automatic adjustment of the pulling force, independent of the design of the cavity. This occur when the traction roller (the sliding element), against the action of spring force, changes its orientation from its maximum angle position relative to the longitudinal axis of the apparatus, and to the position where it is perpendicular to the longitudinal axis. Then the apparatus rotates with the wheels running so the propulsion of the apparatus becomes zero. Thus if the mass of the tool to be pulled and/or be pushed becomes too large, one avoids the apparatus being exposed to overload. The contact point of the traction roller towards the pipe wall moves in a non-slipping revolving movement around the pipe wall.
It has no consequences either the cavity is angular or round, and the diameter may be changed continuously as long as it stays within the maximum/minimum operation diameter of the apparatus. In contrary to the previously known traction mechanisms, which require uniform holes, this apparatus can go into any kind of holes.
The device according to the invention, does no need any counter torque, due to the fact that its motor rotational torque has internally counter force within the device.
The apparatus may generate high push-/pull forces, it can operate in varying diameters, cope with varying hole geometries, it can automatically vary speed and pull-/push force with regard to the load, and is gentle to the inside wall of the cavity.
The apparatus has a simple construction since it consists of a number roller elements each having similar design, they may be single standing or involve several mounted one after another.
The individual elements may be mutually displaced relative to each other, and perpendicular to the travel direction/longitudinal axis of the apparatus. The roller elements mounted in one assembly will rotate at the same speed.